1. Field of the Invention
Carbides and nitrides of a wide variety of elements provide a great diversity of desirable properties; hardness, conductivity of electricity and heat; catalytic activity-making or breaking of many chemical bonds; electrocatalytic activity in fuel cells. In addition, many of the carbides and nitrides are highly refractory, being chemically inert and stable to exceedingly high temperatures. The carbides and nitrides tend to have high melting points so as to be capable of maintaining a solid phase in a wide variety of systems requiring elevated temperatures. In addition, some of the carbides and nitrides are hard, so as to be useful for grinding or to be used in conjunction with other materials for grinding.
In many of the applications of carbides and nitrides it is desirable to have a high specific surface area. This is particularly true where the carbide or nitride serves as a catalyst or is involved in a system requiring a large contact area, as for example the interaction between a gas phase and a solid phase. The problem of obtaining high specific surface area carbides and nitrides is acerbated with what are known as the non-refractory metals, such as iron. These low melting metals tend to sinter readily, resulting in substantial reduction of the surface area. Therefore, it would be extremely desirable to have a method for preparing carbides and nitrides of high specific surface area, both for the hard and soft metals, as well as other elements.
Description of the Prior Art
Descriptions of conventional carburizing and nitriding processes may be found in Kieffer and Schwarzkopf, Hartstoffe and Hartmetalle, Springer-Verlag, Vienna, 1953; Kieffer and Benesovsky, Encyclopaedia of Chemical Technology, 2nd ed. Vol. 4, p. 70; Vol. 13, p. 814; Wiley (Interscience), New York, 1964; Juza, Nitrides of Metals of the First Transition Series, in Advances in Inorganic Chemistry and Radiochemistry, Vol. 9, Academic Press, New York and London, 1966; Kosolopova, Carbides, Plenum Press, New York, 1971; and Toth, Transition Metal Carbides and Nitrides, Academic Press, New York and London, 1971. References concerned with the production of high surface catalysts include Bohm and Pohl, Troisiemes Journeer Internat. D'Etude des Piles a Combustible, p. 183, P.A.E., Bruxelles, 1969; Sokolsky et al., Elecktrokhimiiya 8, 1745 (1972) and Svata and Zabransky, Z. Colln. Czech. Cehm. Commun. 39, 1015 (1974). Improved processes for enhanced surface tungsten carbide may be found in Ross and Stonehart, J. Catal. 48, 42 (1977) and Mozulewskii et al., Kin. and Kataliz. 18, 767 (1977). Imura et al., Preparation of Catalysts II, Vol. 3, p. 627, Elsevier Scientific Publishing Co., (1979), describe the preparation of high specific surface area molybdenum oxycarbides.